One Fact vs. Multiple Facts

Hello,

I am struggling with a logical dilemma, and will appreciate your advise on the subject.

Let's say I am dealing with Data Model for a store. I have sale transactions on one hand and refund transactions on the other.
I have a 1:1 link between the two types of transactions.
The main dimensions which are setting the granularity of the Facts are the same, however the refund transactions have relationship with additional dimensions, e.g. refund reason dimension.

Should I manage the data of both transaction types in one fact table or should I separate them into two fact tables?
What are the key considerations when deciding on the above?

Thanks,
Anna